Incandescent igniter



Feb., 25, 1936. H. STOLL INCANDESCENT IGNITER Filed Dec. l5, 1934 Patented Feb. 25, 1936l UNITED STATES PATENT OFFICE 2,031,985 mcANnEscEN'r IGNITEB Germany Application December 15, 1934, Serial No. 757,627 In Germany February 19, 1934 'Iv Claims. (Cl. 123-145) This invention relates to an igniter for internal combustion engines, and more particularly to an incandescent igniter for an engine which employs a heavy oil as fuel. In accordance with k the present invention the igniter is of the indirectly heated cathode type, and the heating element is enclosed either in a vacuum chamber or one which is lled with inert gas. The former practice in such igniters has been to operate the heating element in an air iilled chamber. The temperature limit of the heater has accordingly been restricted, and it has been necessary to provide a large heating element in order to obtain sufficient heat on the outer surface of the y cathode. Likewise, the cathode has been large.

In the present invention, the heater may be operated at a much higher temperature, the cathode may be much smaller than formerly, and a high degree of heat is concentrated in a relatively small cathode area. v

An object of the invention is to provide an igniter which is more.. eicient and compact.

Another object is to provide an indirectly heated lgniter in which the heater element may operate at a higher temperature.

Still another object is to provide an indirectly heated igniter in which the heater element operates in a substantially oxygen-free atmosphere. I A further object is to provide an igniter in which a high degree of heat is maintained on a small cathode area.l

Other objects and advantages will be in part specifically set forth and in part will be obvious when the following specification is read in connection with the drawing which shows in cross section an igniter in accordance with the present invention.

Referring inV more detail to the drawing, the letter a represents the tapered metallic body of 40 the igniter, which has a longitudinal bore carrylng a tubular insulating sleeve e. This sleeve forms a gas-tight .joint between body a and an axially extending-inner electrode b, which carries at its upper end electrical terminal fastenings ,f insulated from body aby sleevev e and washer g. The lower ends of electrode b and body a are bored to receive pins h. which carrya heater element c. This element is designed to operate at incandescence and is made of a. high melting point material such as tungsten, molybdenum or the like. The cathode comprises a hollow cap d placed over the lower 4end of the body a element c.

as argon, and a gas tight seal is made at the junctionl of the body aand cathode cap d. Any material having 'a high ainity for oxygen, such as tungsten powder, may be placed inside the cap and any remaining oxygen is bound without 5 forming compounds harmful to the incandescent The cathode cap c is made with a thick endl wall in order to retain heat, and the side walls are relatively thin to obtain a low heat conductivity to body a and so retain as much 10 heat as possible on the end wall. A metal of low heat conducting property is preferably employed in forming the cap.

The placement of the heating element in a vacuum or an atmosphere of inert gas allows ex- 15' tremely high temperatures to be attained without harm to the element. Since the end wall of the cap is positioned as closely adjacent the heating element asis practicable in order to secure an eillcient transfer of radiant heat, the end wall is 20 maintained at a high temperature with respect to the igniter body.

Many modifications and changes may be made by any one skilled in the artwithout departing from the spirit and scope of the invention as de- 25 ned -in the following claims. l

What is claimed is:

1. In an incandescent igniter for internal combustion engines, an indirectly heated cathode, a vacuum chamber adjacent said cathode, and a 30 heating element positioned in said chamber.-

2. In an incandescent igniter for internal combustion engines, an indirectly heated cathode, a chamber lled with an inert gas, said chamber being positioned adjacent said cathode, and a 35 heating element positioned in said chamber.

3. In an incandescent igniter for internal combustion-engines, a n'ietallic` body portion, an electrode 'extending through said body portion, a heating'element-nonnected between said electrode 40 and bbdy portion, a hollow cathode secured to said body portion and forming alchamber for said heating element, a substantially oxygen-ree atmosphere in said chamber, said hollow cathode having thin side Walls and a relatively thick end 45 wall and being formed of a substance having a lower heat conductivity than iron.

4. In an incandescent igniter for internal combustion engines, a heating element, a' cathode spaced from said heating element and receiving 50 radiant heat therefrom, and means for maintaining the atmosphere between said heating element and said cathode at a substantially lower oxygen content than normal air;

5. In an incandescent igniter for internal combus'tion engines, a heating element, a cathode spaced fromsaid heating element, said cathode forming a closed chamber around said 'heating element and receiving radiant heat therefrom, and a material of high oxygen amnity contained in said chamber, `whereby said heating element operates in an atmosphere Ofreducedcontent.

7. In an incandescent igniter for internal combustion engines, a heating element, a cathode spaced from said heating element, said cathode lforming a closed chamber around said heating element and receiving radiant heat therefrom, and a powdered tungsten contained in said chamber, whereby the original oxygen content of said oxygen chamber is reduced and the-oxygen held in the 10 form of a compound.

Y HERMANN -STOLL 

